This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A synthetic version of a lipopeptide that is one of the first compounds to appear in HIV-infected cells was obtained from a commercial company and employed to generate a T cell line, using cells from an HIV patient donor. On further analysis it was found that the synthetically produced version of the targeted lipopeptide was not pure, but in fact a mixture, and further, the targeted lipopeptide was not antigenic, but instead two novel components were found to be antigenic. Mass spectrometric investigations indicate that the new antigenic components are very similar in structure to each other and have structures similar to the intended synthetic structure. Mass spectrometric studies at the BUSM MS Resource included the use of GC/MS, MALDI and ESI Q-o-TOF and MALDI and ESI-FTMS instrumentation, enzymatic digestion and chemical hydrolysis of the known and unknown compounds. The structure has now been solved;synthetic analogs have been prepared and their biological activity has been tested. The manuscript describing this phase of the research was published recently (I Van Rhijn et al., CD1c bypasses lysosomes to present a lipopeptide antigen with 12 amino acids. J Exp Med. 2009, 206, 1409-1422. This publication complements another recent publication that reported on the synthesis and biological testing of CD1a lipopeptide antigens. (DC Young et al., Synthesis of dideoxymycobactin antigens presented by CD1a reveals T cell finespecificity for natural lipopeptide structures. J Biol Chem. 2009, 284, 25087-25096.)